This invention relates to the suspension of an object in space by magnetic levitation and, more particularly to the use of a set of coil assemblies which are symmetrically positioned about a central vertical axis, and are selectively energized, for providing both lift and directional stability to the object. The object, to be referred to herein as a model, consists of permanent magnet material with the magnetization in the direction of the vertical axis. The coil assemblies include a main superconducting coil assembly for providing lift, and sets of control, or gradient, coils for providing positional and directional stability, wherein the control coils are constructed in a flat pie form, and also in a circular cylindrical form. The control coils are located outside of a superconducting coil of the superconducting coil assembly.
The suspension of objects in free space, distant from any physical support, is useful in certain situations for conducting various forms of tests and measurements. Of particular interest herein is the suspension of a model by magnetic levitation under conditions wherein the model can be held essentially motionless and with precise control over the orientation of the model. Furthermore, the system of magnets which is to be employed for holding and orienting the model is to be located at a distance from the model, and below the model, so as to provide unimpeded access to the model for the conduction of experiments and measurements.
A problem arises in that presently available magnetic suspension systems do not provide all of the foregoing features. The problem may be appreciated from the fact that the laws of physics dictate that one cannot generate a field that will keep a permanent magnet, such as that employed in the model, stable in all degrees of freedom if the field source is below the permanent magnet. Therefore there is a need for active control by use of control coils driven with electric currents from a control system. In the past, equilibrium has been obtained by suspending an object from a magnet coil against the force of gravity with the attendant disadvantage that the space above the object is cluttered and may well interfere with utilization of the object.